I highly recommend staying at Kobkul's place, especially if you are interested in having an authentic Thai experience in a "real" neighborhood. Kobkul was so friendly and helpful. She not only answered any question we had, she offered us very helpful advice unsolicited. She told us about a special exhibit that was at the National Museum - and we were very thankful she did.
The morning breakfast, served at 8:30 am, was a true Thai breakfast that we thoroughly enjoyed. Typically it was a bowl with rice, some meat, some veggies, and a wonderful sauce that changed daily - sometimes spicy, sometimes sweet - but always delicious. Often it would also include a small fruit dish of some sort. Also, Kobkul would prepare me a wonderful ice coffee every morning.
The apartment was just as described. The room and entire home is kept very clean. The bed and bedding was very nice and comfortable. The air conditioning worked very well. It is on a busy street, so there is quite a bit of street noise, but I used ear plugs and was fine.
The room was about a 10 minute walk to the metro, which was easy to use, very modern and clean. Very impressive. We took the MRT (metro) to Chinatown one night for street food, which was a crazy (but awesome) experience that Kobkul recommended. Definitely do this if you can - it's unforgettable.
I would not hesitate to stay at Kobkul's place if returning to Bangkok!